Re: (ET) Ariens AMP Mower

["David Roden" <etpost drmm net>]

On 13 May 2009 at 14:51, Theoldcars aol com wrote:

> AGM batteries do not charge well in series. The AGM batteries in this
> are not going to last long. 

A short string of AGMs is not as difficult to keep in balance as the long 
ones used in road EVs.  If they're good quality batteries, well matched, 
are 
kept at a consistent temperature, and the charger has sufficient smarts, 
they should have a reasonable life expectancy.  

In this case, though, I have to wonder what they're thinking.  Why on 
earth 
a 4s 5p pack???  It would be much more economical to use a single string 
of 
4 batteries with sufficient capacity.  

Just out of curiosity, I checked a battery supply website 
(batterymart.com) 
and there I see that 14ah house brand AGM batteries are $37 each, while 
75ah 
batteries are $135 each.  A replacement pack of the larger batteries would 
cost $540,  but a replacement of their 20-battery pack would run $740.  

The single string would have fewer connections to go bad, too.

Besides, that many parallel strings is just asking for trouble.  If one 
battery develops a shorted cell, the other strings will discharge 
themselves 
trying to charge the bum string (I've had that happen in a road EV).

I'm inclined to think that maybe they had a bunch of push-mower batteries 
sitting in the warehouse, so they used those instead of sourcing something 
appropriate for the design.  

So, an energy-wasting hydrostatic trans, a bizarre battery layout ... I 
have 
to wonder whether *anyone* on this project had *any* experience in 
electric 
vehicle design. I hope this isn't a disaster that will give electric 
vehicles and yard tools a bad name.


David Roden - Akron, Ohio, USA

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